ST25R3911B datasheet(37/116 Pages) STMICROELECTRONICS

37 / 116 page

After the transmission is executed, the ST25R3911B receiver automatically starts to observe the RFI inputs to

detect a transponder response. The RSSI and AGC (when enabled) start. The framing block processes the sub-

carrier signal from receiver and fills the FIFO with data. When the reception is finished and all the data is in the

FIFO an interrupt is sent to the microcontroller (IRQ due to end of receive), additionally the FIFO status register 1

and FIFO status register 2 display the number of bytes in the FIFO so that the microcontroller can proceed with

data download.

In case of an error or bit collision detected during reception, an interrupt with appropriate flag is sent.

Transmit and Receive when the data packet is longer than FIFO

In case a data packet is longer than FIFO the sequence explained above is modified.

Before transmit the FIFO is filled. During transmit an interrupt is sent when remaining number of bytes is lower

than the water level (IRQ due to FIFO water level). The microcontroller in turn adds more data in the FIFO. When

all the data is transmitted an interrupt is sent to inform the microcontroller that transmission is finished.

During reception situation is similar. In case the FIFO is loaded with more data than the receive water level, an

interrupt is sent and the microcontroller in turn reads the data from the FIFO.

When reception is finished an interrupt is sent to the microcontroller (IRQ due to end of receive), additionally the

FIFO status register 1 and FIFO status register 2 display the number of bytes in the FIFO that are still to be read

out.

Anticollision – ISO 14443A

Note:

For this section, it is assumed that there is more than one ISO/IEC 14443A PICC in the reader RF field, and all

of them are compatible with ISO/IEC 14443 up to level 4.

This section describes the anticollision procedure of ST25R3911B for ISO14443A tags. After an ISO14443 type A

tag enters in the reader field, the reader has to perform a selection process that brings it into the PROTOCOL

state in which the actual application implemented in the tag can be executed. This selection process is described

in the ISO/IEC 14443-3. Figure 21 shows the states that a tag and a reader have to pass through to enter the

protocol state.

The selection procedure starts when a PICC enters the reader field and the PCD sends a REQA (or WUPA)

command followed by an anticollision procedure (including SELECT, RATS and PPS).

ST25R3911B

Application information

DS11793 - Rev 6

page 37/116

ST25R3911B Datasheet(PDF) 37 Page - STMicroelectronics